1. Field of the Invention
The present invention relates to a radar apparatus installed in a vehicle or the like.
Priority is claimed on Japanese Patent Application No. 2005-366547, filed Dec. 20, 2005, the content of which is incorporated herein by reference.
2. Description of the Related Art
Generally, a radar apparatus has: an antenna part for transmitting radio waves to space, and receiving reflected waves from space; a wireless part for generating a high-frequency signal supplied to the antenna part, and converting a reflected high-frequency signal to a medium-frequency signal; and a circuit part for controlling the high-frequency signal and processing the medium-frequency signal.
In such a radar apparatus, electric power consumption of the wireless part is large, and heat is generated when the wireless part operates; thus, the heat generated at the wireless part should be dissipated. Generally, the wireless part is connected to an antenna, a body of the apparatus, a heat sink, or the like, so as to dissipate the heat.
When the above-described radar apparatus is installed in a vehicle such as an automobile or the like, the apparatus should be miniaturized so as to improve conditions or convenience for the installation. Therefore, a radar apparatus has been proposed which has the antenna part employing a planar antenna (see, for example, Japanese Unexamined Patent Application, First Publication No. 2005-20525).
In such a radar apparatus, the thickness of the planar antenna itself can be reduced, so that the depth of the radar apparatus can be reduced so as to miniaturize the apparatus.
With respect to the heat removal, the planar antenna is prepared as a slot antenna using metal parts, in which side walls of its waveguide are used as fins, and the planar antenna, the wireless part, and the circuit part are positioned in an integral contact manner. Therefore, heat generated at the wireless part and the circuit part can be transmitted directly to the planar antenna due to heat conduction, and the heat is emitted to the outside via a number of fins, without employing a heat sink or the like.
However, in the above conventional slot antenna, the width of each slot opening is very small so as to control the amount of radiation through each slot. Therefore, air-permeability is inferior, and it is impossible to efficiently emit heat from the side walls of the waveguide. Accordingly, if the heat generated by the wireless part is large, an additional heat emitting member must be provided.